Q32
Neeraj has a rectangular field of size 20 × 40 sq.m. He has to mow the field with a mowing machine of width 1 m. If he mows the field from the extremes to the centre, then the number of rounds taken by him to mow half of the field will be
Answer: B
The movement of the mower may be considered as shown in the figure.
Total area of the plot = 20 × 40 = 800 sq.m.
After 1st mowing, area left = (20 – 2) × (40 – 2) = 684 sq.m.
After 2nd mowing, area left = (20 – 4) × (40 – 4) = 576 sq.m.
After 3rd mowing, area left = (20 – 6) × (40 – 6) = 476 sq.m.
After 4th mowing, area left = (20 – 8) × (40 – 8) = 384 sq.m.
∴ Half the area is mowed between 3 to 4 rounds.
∵ 476 − 384 = 92 sq.m.
Hence, option (b).